Education

1. Fetal
Development
Growth &
monitoring

2. Stages of Fetal Growth
The Zygote - in fallopian
tube, conception to 2 weeks
The Embryonic Stage - in
placenta, 2 weeks to 2 months
The Fetal Stage - in placenta, 3
months to 38-42 weeks at birth

3. 1. The Zygote
Pre-implantation Embryo
 Egg fertilized in fallopian tube
 Cell division occurs without
increasing cell size
(hyperplasia)

4. Blastocyst (conceptus)
 Forms – a single layer of cells
form hollow sphere
 Inner cell mass becomes fetus
and amniotic fluid
 Outer cell mass becomes
trophoblast and placenta

5. Endometrium
The uterine wall where blastocyst
implants
 By day 4 the blastocyst or
conceptus arrives in uterus
 By day 10 implantation occurs
 At 2w conceptus becomes
embryo

6. 2. Embryonic Stage
 Lasts from 2 weeks to 2 months;
baby is 1 1/2 inches long;
 Period of massive cell
differentiation and synthesis
 Initially cell number doubles every
24 hrs

7. Embryonic layers
Ectoderm – outer layer
 forms brain,
 nervous system,
 hair,
 skin

8. Mesoderm – middle layer
Forms muscles, internal
organs, bones, CV and
excretory systems
Endoderm – inner layer
Forms glands, endothelial layer
of digestive, respiratory and
excretory systems

9. Embryonic Stage
 Hyperplasia – increase in cell
numbers
 Hypertrophy – increase in cell
size

Both processes are important for
organ growth and development.

10. Embryonic Development
What happens as the baby develops?
Month 1
 organs blocked out,
 heart beating,
 neural tube, which becomes brain and
spine, begins to form,
 At 6 weeks liver begins to form RBC

11. What happens as the embryo develops to
fetus?
Months 2-4
 At 2 months minute organ details
established; 1" long,<1oz.
 First obstetric Ultrasound
7 weeks–confirm pregnancy, exclude
ectopic or molar pregnancies,

12.  confirm cardiac pulsation and
measure the crown-rump length
for dating.
 CNS and GI tract almost
complete;
 Fingers and toes well defined;

13. 4-months
 organ formation nearly
complete

14. Early Ultrasound
 The gestational sac can be seen at 4½
weeks gestation and the yolk sac at 5
weeks.
 The embryo can be observed and
measured by about 5½ weeks.
 Very importantly confirms the site of
the pregnancy is within the cavity of
the uterus.

15. 3. Fetal Development
Month 3
 Spleen, lymphoid cells and BM with RBC,
WBC
 Can hear baby's heartbeat
 Sex organs appear
 Hands fully formed

16. Blood Flow
 The use of color flow mapping can
clearly depict blood flow in fetal
blood vessels in a real time scan,
flow direction represented by
different colors.
 'Color' doppler indispensable in
diagnosis and assessment of
congenital heart abnormalities.

17. Month 3-4
 Peripheral reflexes; Placenta fully
formed; Fetus begins to move;
 Eyes, ears, nose and mouth
approach typical appearance;
 Begin nerve myelinization
(complete at 1 year); 6-7", 5 oz.

18. Month 5
 Fetus ingests and absorbs large
quantities of amniotic fluid;
 Kidneys excrete urine;
 Sleeps and wakes at regular
intervals;
 May have hair; eyelids still fused;8-
12", 1/2 to 1lb.

19.  18-20 Week Ultrasound
Midpoint Ultrasound
At 18–20 weeks
1. look for congenital
malformations,
2. exclude multiple pregnancies
3. to verify dates and growth

20. Months 6-9
GI function approaches newborn;
6-months
 fingerprints;
 can survive in NBU

21. 7-months
 sucks thumb;
 responds to light and sound;
 gains ½-1 oz/d
8-months
 growth continues;
 begins to store nutrients

22. 9-months
 gains ~ ½ lb/week;
 lungs finally developed

23. Terms: Fetal/Infant Growth
 Prenatal–conception to birth
(gestation)
 Perinatal–from 27weeks to
birth or shortly after birth
 Postnatal – after birth

24.  Neonatal – birth–4weeks
 Preterm – born before
38weeks
 Term – born 38-42weeks
 Post term – born more than
42weeks gestation

25.  Concept of Critical
Development Periods
 Vulnerable Periods During
Fetal Development

26.  First 8weeks important to
avoid exposure to toxins
including excessive intake of
vitamin A
 Time when CNS, CV, neural
tubes, limbs, face
development begins

27. Vulnerable Periods During
Fetal Development
 Neural tube defects:2-4 weeks
post conception;
 Caused by genetic, nutritional
or environmental factors;

28.  Recurrence of NTD reduced with
folic acid supplementation; vitamin
B12 may also be needed;
 Studies have also related
methionine deficiencies and
elevated homocysteine levels to
NTD.

29. Critical Development
Periods Role of Placenta
 Lifeline from mother to fetus
 Performs respiratory, absorptive,
excretory functions
 Placental development dependent
upon maternal nutrition
 Fe-def. anemia affects O2 supply
to fetus

30. The Role of the Placenta
 Lifeline of the mother to her
baby;
 necessary for the fetus to reach
full potential.
 Performs respiratory,
absorptive, and excretory
functions for the fetus.

31.  Maternal malnutrition limits
placental development and
reduces placental blood flow
which decreases the transfer of
energy and essential nutrients
to the fetus, thus limiting his/her
full genetic potential.

32. 1. Placental Structure
and Development
 Placenta develops from the
trophoblast (outer cells of
blastocyst);
 Forms villi into maternal blood pool
through endometrium into
maternal blood pool and
interweaves fetal and maternal
blood;

33.  The umbilical cord (formed
from umbilicus) extends to
placenta;
 Placenta maintains 2
completely different blood
supplies.

34. 2. Mechanisms of Placental
Nutrient Transfer
*Passive diffusion
Nutrients move from area of higher
concentration to one of lower
concentration.

35. Nutrients
 O2 & CO2,
 FA,
 fat-soluble vitamins,
 steroids,
 nucleosides,
 electrolytes,
 water

36. *Facilitated diffusion
 Nutrients move from greater to
lesser concentrations on a carrier;
 is faster than passive diffusion.
 Nutrients
1.glucose and
2.other monosaccharides.

37. *Active transport
 requires a protein carrier to move
nutrient against electro-chemical
gradient.
Nutrients
1. Ca, P, Mg, Fe, I,
2. glucose,
3. water-soluble vitamins,
4. amino acids

38. *Solvent drag
movement of ions with water
as it flows across membrane
- electrolytes

39. *Pinocytosis/endocytosis/
phagocytosis
Placental cell engulfs nutrient, forms
vacuole to enter fetal blood supply.
 Nonspecific proteins, IgG,
 maternal immunoglobulin to give
fetus resistance to infections.

40. Placental Nutrient Transfer
Regardless of the transfer method
the process is complex due to the
two different blood supplies and
the dual membranes
- fetal endothelial cells and
- placental membrane)

41. Most proteins do NOT cross the
placenta
Exception; immunoglobulin IgG to
help with fetal immunity.

42. Respiratory and Excretory
Exchange
RBC carry O2
 maternal RBC have decreased
affinity for O2;
 fetus increased affinity;
 Mother compensates by increased
Cardiac Output and respiration rate;

43.  CO2 and waste through umbilical
cord to placenta to maternal
blood;
 Placenta freely permeable to CO2,
H2O, urea, creatinine, uric acid

44. These wastes are transported:
 CO2
– simple or passive diffusion
 Urea, creatinine, uric acid
– facilitated diffusion or active transport

45. Placenta Metabolism
 Produces 60 enzymes,
 Synthesizes proteins and fatty
acids,
Metabolizes glucose for its own
needs,
1. actively transfers glucose to fetus;
2. Stores glycogen.

46. Placental Hormones
A. Peptide Hormones

47. 1.*Human chorionic
gonadotrophin (HCG):
 high levels early on,
 decreases after 10 weeks;
 helps implantation of blastocyst,
 used for early pregnancy testing.

48. 2.*Placental lactogen:
 Starts low,
 increases in 3rd trimester;
Functions
a. Stimulates growth of mammary
glands to prepare for breast feeding.

49. b. Inhibits insulin's action on
adipose and muscle tissue to
keep amino acids, glucose and
fat in circulation to support fetal
and gland activity.

50. B. Steroid Hormones
1.*Estrogen (estriol):
Begin to be produced in free floating
blastocyst;

51. Function:
 Facilitates implantation;
 Increases lipid formation and
storage;
 Increases - protein synthesis,
- uterine blood flow;

52.  Promotes ligament flexibility (helps
cervix to dilate);
 Prompts breast development;
 Can make tissue hydrotropic by
increasing water retention (edema,
ankles swell, face puffy).

53. 2. Progesterone
 Helps sustain pregnancy;
 Synthesized from maternal
cholesterol;

54.  Relaxes smooth muscle
- in blood vessels,
- GI and urinary tract,
- in uterus to facilitate
fetus growth;
 Favors maternal fat deposition;
 May decrease peristalysis with
resulting constipation

55. Fetal Body Composition
 Marked changes during
pregnancy
 General trend à progressive
increases in fat, protein and
mineral content
 Most dramatic changes in last
4—5weeks

56. Affect of Poor Nutrition on
Critical Periods
Consequences of Fetal
Malnutrition
SGA
newborn weight < 10th percentile
for gestational age

57. dSGA
 head circumference and skeletal
growth (length) normal;
 poorly developed muscles and
subcutaneous fat

58. pSGA
 all body parts proportional
 At Zygotic/Embryonic Stage à no
implantation;
 miscarriage; birth defects,
 inborn errors of metabolism,
 brain cell formation

59.  At Fetal Stage à low birth weight,
limited genetic potential,
 brain cell formation